The present invention relates to a buckle unit for seat belt to be provided on a seat in an automobile or other vehicle.
As present, seat belt is furnished on the seat of automobile and other vehicle for the purpose of protecting occupants of the vehicle from collision. To facilitate the procedure to remove or put on seat belt of this type, a buckle unit is usually provided, which generally comprises a latch member with a claw to engage with a tongue, and the latch member is pushed by a spring toward the direction to engage with the claw.
In such case, if resilient force of spring against the latch member is decreased in order to reduce the operating force at the release, the engaging force between the tongue and the latch member becomes weaker. When heavy crash such as vehicle collision occurs, the latch member is displaced by inertia, and the tongue is withdrawn from the buckle, i.e. the so-called inertial withdrawal is very likely to occur. To cope with this problem, spring force to the latch member had to be increased in order to prevent such inertial withdrawal. This leads to the undesirable increase of operating force necessary for the release of the engagement of the above buckle, and there have been strong demands on the alleviation of the operating force.
To solve such problem, it has been proposed to offer such buckle unit that a locking member is slidably mounted to hinder the displacement during the engagement of the tongue with the latch member on the buckle side so that the latch member is not moved toward the direction to unexpectedly separate from tongue by inertia force caused by heavy crash. Such units are disclosed in the Japanese Utility Model Publication No. 64-87, the Japanese Provisional Utility Model Publication No. 63-88108, the Japanese Provisional Utility Model Publication No. 60-139560, etc.
As an example, the buckle unit of the Japanese Provisional Utility Model Publication No. 60-139560 is shown in FIG. 15 and FIG. 16.
In these figures, 1 represents a tongue, which has a belt connecting hole 2 on one end and an engagement hole 3 on the other end. On the other hand, 4 is a frame of the buckle main body A, in or from which the above tongue 1 is inserted or detached. The buckle main body A is assembled on said frame 4 as its base.
The above buckle main body A comprises said frame 4, the latch member 5 to be connected with said frame 4 as base, a locking member 6 to control the movement of said latch member 5, an operating member 7 moving slidably, an ejector 9 to eject the released tongue 1 from the frame 4 by spring 8, and a cover member 10 to cover the buckle element, which comprises the above members and components.
The frame 4 is formed in U-shape, comprising a bottom plate 4a and lateral walls 4b and 4c running upward from both sides of the bottom plate 4a. On the lateral walls 4b and 4c, the following members and components are sequentially provided from the portion where the tongue 1 is inserted toward the depth: fan-shaped windows 12 and 12', into which the extended portions 11 and 11' extending in transverse direction from both sides of the latch member 5 are to be inserted, and fulcrum holes 14 and 14', into which the support shafts 13 and 13' protruding on the sides of the latch member 5 are supported. Further, on upper backward portion of lateral walls 4b and 4c, notches 17 and 17' are provided, where spring support plate 16 is supported in cooperation with the open hole 15 on the bottom plate 4a.
On the fan-shaped windows 12 and 12', projections 19 and 19' are furnished, which can be engaged in the open holes 18 and 18' on the extended portions 11 and 11' downward from above. The end surfaces 12a and 12a' of the fan-shaped windows 12 and 12' where the tongue 1 is inserted are placed face-to-face to the shoulders 11a and 11a' of the extended portions 11 and 11' of the latch member 5 with a slight gap between them so that, when the vehicle is collided, the tensile load applied on the latch member 5 is directly transmitted to the frame 4.
At the center of the frame bottom plate 4a, an opening is formed continuously with the open hole 15 for movably guiding the ejector 9 by both edges along the direction to insert or remove the tongue 1. On the front end of the opening 20, a guide rod 20a to be inserted into the guide hole 9a of the ejector 9 is protruding from the direction of the insertion of the tongue 1. On the spring support plate 16 placed face-to-face to this guide rod 20a, a spring receptacle 21 to support the fixed end of the spring 8, which pushes the ejector 9, is furnished. Further, a belt connecting hole 22 is furnished on the bottom plate 4a behind the open hole 15.
The latch member 5 is bent in L-shape on the axial line of the support shafts 13 and 13'. At lower center of the latch portion 5a in parallel to the frame bottom plate 4a, a claw 23 to be connected to the engagement hole 3 of the tongue 1 is provided. Between the back plane of the lever unit 5b, vertically rising from the support shafts 13 and 13' and the spring support plate 16, latch portion 5a is pushed at all times toward the direction "X" (shown by an arrow in FIG. 16) by resilient force of compression spring 24 toward the direction approaching the frame bottom plate 4a around the support shafts 13 and 13'.
The locking member 6 is integrally provided with two movement stoppers 25 and 25' in such size as to close the open holes 18 and 18' of the latch member 5 on both sides, and these are slidably mounted on upper surface of the latch portion 5a of the latch member 5 with the predetermined stroke along the inserting or removing direction of the tongue 1. By a tension spring 28, furnished between the hook 26 formed by bending upward from the center of the locking member 6 and the hook 27 formed on front end of the latch member 5, the locking member 6 is pushed permanently toward the direction to detach the tongue against the latch member 5, i.e. in the direction "u" (as shown by an arrow in FIG. 16.).
On the other hand, the front end surface of the operating member 7 is a pressure surface 7a capable to perform pressing movement, and the rear end surface is a lever touching surface 7b to touch the front surface of the lever portion 5b of the latch member 5. Further, the vertical surface is a touching surface 7c to touch the touching part 29 of the locking member 6. The operating member 7 is guided by two guide rods 30 and 30', which are horizontally protruding from spring support plate 16 and is slidably movable in the inserting or removing direction of the tongue 1. Further, the operating member 7 is pushed permanently in the direction "u" by two springs 31 and 31', which are engaged on outer periphery of the guide rods 30 and 30' on the spring support plate 16.
The positional relationship between the lever touching surface 7b and the locking member touching surface 7c is such that, during the pressing operation, the locking member touching surface 7c comes into touch with the locking member 6 at first and the locking member 6 is slided toward the direction "v" (shown by an arrow in FIG. 16). When the movement stoppers 25 and 25' of the locking member 6 release the open holes 18 and 18' of the latch member 5, the lever touching surface 7b comes into touch with the lever portion 5b of the latch member 5 to start to tilt the latch member 5.
The marginal portions of the pressing surface 7a of the operating member 7 are surrounded by the cover member 10 in almost the same plane, and this prevents unexpected release of the buckle engagement when elbow of the passenger touches the operating member 7.
Further, the ejector 9 mounted on the frame bottom plate 4a is designed in such manner that it can be displaced within the predetermined sliding range by the insertion or removal of the tongue 1. The sliding range of its front end is set in such manner that the rotating of the latch member 5 toward the direction to engage with the tongue 1 is hindered, and that at least a part of it lies between the claw 23 of the latch member 5 and the frame bottom plate 4a at the end of the pushing movement of the tongue 1.
The front end on the top of the latch member 5 is provided with a pair of projections 32 and 32', by which the forward movement of the locking member 6 is limited.
The spring guide rod 33 protruding from spring support plate 16 has oblong and flat tip, from which a slit 34 is formed along the center. On outer surface of the tip, fall-stop projections 35 and 35 are furnished to engage with the free end 24a of compression coil spring 24, and the tip of the guide rod 33 is inserted into the oblong notched portion 36 provided on the lever 5a of the latch member 5.
On the other hand, the ejector 9 has a hole 39 at the end surface to receive one end of the spring 8. Near the opening of this hole 39, a pin hole 38 is provided, into which the pin 37 is inserted into the direction perpendicular to the hole 39. Spring 8 is compressed and is accommodated in the hole 39, and the pin 37 passing through the pin hole 38 is used to receive and hold the compressed spring 8. After the fixed end of the spring 8 is brought into contact with the tip of the spring receptacle 21 of the spring support plate 16, the pin 37 is removed, and spring 8 is stretched. Thus, the fixed end of the spring 8 is engaged in the spring receptacle 21.
In the buckle unit with such arrangement, when the tongue 1 is inserted into the buckle main body A in the arrow direction "w" with the tongue in the preparation status shown in FIG. 16, the ejector 9 is pushed by the tip of the tongue 1, is moved backward, and is retreated from lower portion of the claw 23 of the latch member 5. The latch member 5 is rotated in the direction of the arrow "X" around the support shafts 13 and 13' by the action of compression coil spring 24, and the claw 23 is engaged with the engagement hole 3 of the tongue 1. As the result, the tongue 1 is engaged with and connected to the buckle main body A.
In this case, the movement stoppers 25 and 25' of the locking member 6 are separated from the backside of the projections 19 and 19' as the latch member 5 is rotated and displaced, and they are further moved in the direction of the arrow "u" by the action of the tension spring 28. Because the movement stoppers 25 and 25' close the open holes 18 and 18' of the latch member 5, the projections 19 and 19' are hindered from entering into these open holes 18 and 18'. Therefore, in case abnormal impact is applied such as the vehicle collision, the rotating of the latch member 5 in the direction of the arrow "Y" is restricted because the top surfaces of the movement stoppers 25 and 25' are in touch with the lower ends of the projections 19 and 19', and the latch member 5 is held at the lower position. As the result, the separation of the tongue 1 from the buckle main body A is prevented.
Next, in case the tongue 1 is separated from the buckle main body A, the pressing surface 7a of the operating member 7 is pressed by finger in the direction of the arrow "v." Then, the locking member touching surface 7c of the operating member 7 is engaged with the touching portion 29 of the locking member 6, and the locking member 6 is displaced in the direction of the arrow "v" against the resilient force of the tension spring 28. For this reason, the stoppers 25 and 25' move from above the open holes 18 and 18' of the latch member 5, allowing the projections 19 and 19' to enter the open holes 18 and 18'. Then, the lever touching surface 7b pushes the lever member 5b of the latch member 5, and is rotated in the direction of the arrow "Y" against the resilient force of compression coil spring 24. Therefore, the latch member 5 is separated from the buckle main body A as the tongue 1 is pushed by the ejector 9 as soon as the claw 23 is moved upward and is withdrawn from the engagement hole 3 of the tongue 1. The latch member 5 is held at the saving position above until the ejector 9 touches the lower surface of the claw 23 of the latch member 5 and the tongue 1 is inserted. When the pushing force on the operating member 7 is cancelled, the operating member 7 is moved in the direction of the arrow "u" by the force of the springs 31 and 31' and returns to the initial position as shown in FIG. 16.
In this way, the tongue 1 can be easily engaged with or separated from the buckle main body A.
Incidentally, the direction of the impact force caused by collision differs according to the conditions of each collision, and the impact force may act in the direction to insert the tongue into the buckle. Thus, it is necessary to take proper measures against the impact force working toward the direction to insert the tongue. For this purpose, the force of the springs 31 and 31' to push the operating member 7 and the force of the tension spring 28 to push the locking member 6 are increased. As the result, even when impact force works in the direction to insert the tongue, the operating member 7 and the locking member 6 are not moved by inertia because the force of springs 31 and 31' as well as that of the tension spring 28 are strong enough. Accordingly, the tongue is not withdrawn from the buckle, i.e. so-called inertial withdrawal is prevented.
However, the increase of the spring force of the tension spring 28 and springs 31 and 31' results in heavier operating touch and in poor improvement of operating feeling as in the cases of the buckles of the conventional type. Because strong resilient force is required, although not so strong as in the case of the conventional type buckle, the problem also arises with higher cost of tension spring 28 and the springs 31 and 31'.